The invention relates to devices for shrinking collagen in body tissue. More particularly, the invention relates to catheter devices for shrinking the chordae tendineae of the heart.
The human heart consists of four muscular chambers: the right atrium, which connects to the right ventricle, and the left atrium, which connects to the left ventricle. The pumping action of the heart is achieved by contraction and relaxation of the heart muscles. The filling stage of the heart cycle is called diastole. The pumping stage is called systole. Both atria are filled at the same time during diastole and both ventricles expel their blood at the same time during systole.
During diastole, the heart chambers are at their largest volumes, and the atrioventricular valves, which separate the atria from the ventricles, are open. During systole, the heart muscles of the atria contract first, forcing their contents into the ventricles, and then, as the ventricles begin to contract, the increased ventricular pressure forces the atrioventricular valves to close, and the semilunar valves into the arteries to open, so that blood flows out of the heart and into the body tissues. Oxygen depleted blood is forced from the right ventricle into the lungs through the pulmonary artery, and oxygen rich blood is forced from the left ventricle into the remainder of the body through the aortic artery.
Each atrioventricular valve is composed of leaflets of connective tissue, called cusps, which are connected to the heart muscle tissue at the annulus of the aperture between the atrium and the ventricle. The unconnected portions of the cusps overlap with each other when the valves are in the closed position, such that the aperture between the chambers is completely closed. The cusps are stabilized and operated by roughly conical shaped muscles extending from the floor of the ventricles, called papillary muscles, which are connected to the cusps by fibrous, tendon-like structures called chordae tendineae (chordae). There is at least one papillary muscle for each cusp. The chordae begin at the apex of the cone of the papillary muscle and fan upward roughly to the periphery of the cusp. The chordae tendineae are the xe2x80x9cguy wiresxe2x80x9d for the cusps of the atrioventricular valves. The mitral valve, between the left atrium and ventricle, has two cusps, while the tricuspid valve, between the right atrium and ventricle, has three cusps.
The pumping efficiency of the heart can be greatly diminished if the atrioventricular valves malfunction, allowing leakage of the blood from ventricle to atrium. A particularly common problem is weakening or stretching of the chordae, which condition allows the cusps of the affected atrioventricular valves to prolapse into the atrium during systole. Valve prolapse lowers the pumping efficiency of the heart by allowing a portion of the blood to flow in the wrong direction. Valve prolapse is particularly common with the mitral valve, a condition known as primary mitral valve regurgitation, but can also occur with the tricuspid valve. Other conditions which cause mitral valve malfunction include excessive lengthening or thickening of the cusps and the annulus of the valve becoming stretched or loose. Malfunction of the mitral valve occurs in an estimated 1.4% of the population and can lead to a variety of problems, including weakness, persistent nausea, atrial or ventricular fibrillation, a greater risk of infective endocarditis, congestive heart failure, and increased risk of sudden death.
Co-owned U.S. Pat. No. 5,989,284 to Laufer discloses a method of treating primary mitral value regurgitation by applying thermal energy to shorten the chordae. The method of Laufer involves insertion of a catheter into the ventricle of the heart, and placing the tip of the catheter in contact with the chordae. Shortening of the chordae can prevent prolapse of the atrioventricular valve cusps.
The chordae of the human heart are composed predominantly of tightly coiled strands of collagen. Application of heat to the chordae, raising the temperature of the tissue to about 50-55xc2x0 C., causes the collagen strands to uncoil and straighten. Upon cooling the collagen resumes its tightly coiled shape, however, the collagen strands tend to entangle with one another, causing the total volume of the collagen, and thus the chordae, to shrink. Shrinkage of the chordae can be an effective treatment of primary mitral regurgitation and the related problem of tricuspid valve regurgitation. Likewise, heating the cusps or the annulus, which also contain collagen, to about 50-55xc2x0 C., causes the collagen therein and the cusps or annulus to shrink in size and length.
The present invention provides catheter devices for shrinkage of tissue, such as the chordae, cusps or annulus of valves of the human heart and other tissues, such as the esophagus in the area of the sphincter or the female urethra below the bladder. Heat is applied to the target tissue via a heat transfer means on the catheter tip. The method of Laufer is a minimally invasive means of treating mitral regurgitation, however, appropriate placement of the catheter tip, and keeping it in place can be difficult, particularly in a moving organ, such as the heart.
In some applications, it is possible to visualize the tissue during laser treatment by means of an endoscope. This is not possible in a beating heart, due to the opaque nature of blood. In addition, the chordae are difficult to visualize by ultrasonic or x-ray techniques, thus, application of energy to the chordae, as in the method of Laufer, must be performed xe2x80x9cblind.xe2x80x9d A similar problem exists in treatments of female stress incontinence (FSI) involving thermal shrinkage of the tissue surrounding the urethra below the bladder. The small diameter of the urethra (about 1.5 to 5 millimeters) makes endoscopic viewing difficult. It would also be beneficial to shrink tissues such as the esophagus in the area of the sphincter to treat gastro-esophageal reflux disease (GERD).
It would be desirable to be able to shrink the chordae tendineae of the heart and other tissues in a minimally invasive, non-surgical catheterization procedure that would allow precise and stable placement and application of energy to the tissues. It would also be desirable to provide a treatment that could be rendered in a few minutes in a hospital cardiac catheterization laboratory or outpatient department or an outpatient surgical center, with little recuperation time.
A catheter device suitable for shrinking chordae tendineae of the human heart is provided with an energy conduit (e.g., an optical fiber, electrical conducting cable, or other similar energy transmitting device) and a positioner device that facilitates the delivery of thermal energy to a predetermined region of the chordae tendineae.
In a preferred embodiment, a catheter containing an optical fiber, having a distal end portion encompassing a directional energy emitting device within an asymmetrically-shaped balloon, positions the energy conduit and directionally delivers energy to tissues. The asymmetric shape of the balloon allows an operator to precisely determine the orientation of the device within the tissue using ultrasound or x-ray imaging, for example. The distal end of the catheter is closed and has a blunt shape. The distal end portion of the catheter within the balloon contains an aperture that admits inflation fluid into the balloon, and directs the energy emission from optical fiber through only one portion of the asymmetric balloon. Thus, by imaging the inflated balloon within the tissue, the operator can determine the direction of laser energy emission.
In another embodiment of the present invention a fiber optic cable or other thermal energy delivery device is contained within a tubular sheath that is open at its distal end, such that laser or other thermal energy can be emitted by the cable through the distal opening of the sheath. Also present within the sheath is a flexible metal positioner and stabilizer rod, having a hook-shaped distal end portion and a blunt, atraumatic distal end. The blunt end of the flexible metal positioner and stabilizer rod can be in the form of a ball or other similar form, which will tend to slide off, rather than penetrate tissue when the end of the rod comes into contact with the tissue.
The hooked distal end portion of the rod is helicoid, i.e., having a configuration that approximates that of a helical coil. The length of the distal end portion is approximately 3 to 6 times the radius of curvature of the coil, i.e., the end portion comprises roughly one half to one loop of the helical coil. Both the cable and the rod are independently slidably moveable within the sheath. The distal end of the fiber optic cable can be retracted into or extended out of the distal opening of the sheath, and, independent of the cable, the hooked distal end portion of the flexible rod can be withdrawn into the sheath or extended therefrom.
The flexible metal rod can be preferably composed of a superelastic shape-memory alloy such as nitinol, which has been previously formed into its hooked shape by bending the distal end portion of the rod into a helical-coil shape and heat-treating the bent portion of the rod at a temperature of about 300xc2x0 C. to 800xc2x0 C. to fix the shape. When the distal end portion of the rod is retained within the sheath, the end portion of the rod straightens due to pressure from the relatively more rigid sheath. When substantially extended from the distal opening of the sheath, the flexible rod returns to its helical-coil/hooked shape. The distal end portion of the rod can be repeatedly coiled and uncoiled by extending the end portion out of or into the sheath, respectively, due to the shape-memory properties of the superelastic alloy.
The sheath portion of the catheter device defines one or more lumens in which the energy conducting cable and flexible rod are disposed. In a preferred embodiment of the invention, the flexible sheath defines two lumens, the energy conducting cable being situated in a first lumen and the flexible rod being situated in a second lumen. In addition, there can be other lumens within the sheath, for example, there can a lumen for a guide wire, commonly used to position a catheter within a specific area of the anatomy, or a lumen for delivery to, or withdrawal of fluids from, the irradiation site. Alternatively, the catheter device of the present invention can have a sheath with a single lumen, wherein the rod and cable are positioned side by side in the same lumen, through which fluid can also be infused or withdrawn.
The proximal end of the flexible sheath can be attached to a handpiece to provide the operator of the device a method of controlling the position and orientation of the device. The handpiece can include a mechanism or mechanisms for manipulating either the flexible rod, the energy cable, the sheath or any combination thereof.
The energy conducting cable extends throughout the whole length of the device, generally exiting the device at the proximal end of the handpiece and extending further to a coupler at the proximal end of the cable, adapted for connection to an energy source. When the energy source is a laser generator, the coupler is an optical coupler, and the cable comprises at least one, and preferably several optical fibers. A plurality of optical fibers can be bound together in a sleeve or wrapped in a plastic film, such as shrink-wrap, to protect the fibers and create a single optical cable.
Alternatively, the cable can comprise one or more insulated wires, adapted at their proximal end for connection to an electrical power or radiofrequency (RF) energy source. The distal end of each wire, located in close proximity to the distal opening of the sheath, is adapted for connection to a variety of energy emitting devices, such as electrical resistive heating loops, ultrasonic generators, microwave generators, RF electrodes, and the like. The individual wires are preferably bound together as described for the optical cable above.
Optionally, a slidable control button or lever, which can be engaged by the operator""s thumb, is disposed within a slide channel on the exterior of the handpiece. The portion of the button which extends through the slide is attached to a metal sleeve which, in turn, is attached to and surrounds the energy conducting cable. When the button is advanced a predetermined distance, an audible xe2x80x9cclickxe2x80x9d can be created by an optional ratchet mechanism, and the energy cable is extended a like distance out of the distal end of the sheath in which it is disposed. A similar mechanism can be used to control the extension and retraction of the flexible metal rod to deploy the hooked distal end of the rod or to manipulate the position of the sheath relative to the energy cable or rod. Alternatively, the rod, sheath and/or energy cable can be manipulated by a rotatable knob attached to a shaft, which shaft is operably attached to the energy cable, the sheath, or the rod in a manner such that the cable, rod or sheath can be slidably moved distally or proximally by turning the knob. In an alternative embodiment, the operator can optionally deploy the flexible metal rod or cable by grasping the proximal end of the rod or cable and manually sliding the rod or cable forward or backward a predetermined distance.
In use, an operator positions the distal end of the sheath within a ventricle of the heart, in close proximity to a papillary muscle, with both the distal end portion of the rod and the distal end of the cable substantially retracted into the sheath. The operator can guide the device into its desired position by inserting it over an earlier placed guide wire, can thread the device through a tubular catheter that has been pre-positioned in the heart, by articulating the distal end portion of the sheath or by any other acceptable method known in the medical art. After proper positioning, the distal end portion of the rod is then slid forward to gradually extend the end portion of the rod from the distal end of the sheath. As the distal end portion of the rod becomes less constrained, it gradually resumes its curved shape, and can thus encircle the papillary muscle and then be manipulated up to encircle the chordae tendineae that are attached to the papillary muscle.
After the rod has encircled the chordae, the operator extends the distal end of the energy cable out of the distal opening of the sheath, placing the distal end of the cable in close proximity to, or in contact with the chordae. The hooked end of the rod acts as a stabilizer for the distal end of the catheter device. Thermal energy, in the form of coherent light (laser), ultrasound, microwave, RF energy, or heat generated from an electrical resistive heating coil is supplied to the chordae, by the energy cable, in a quantity sufficient to raise the temperature of the collagen in the chordae to about 50 to 55xc2x0 C., causing the collagen strands to uncoil. When the emission of energy is ceased, the chordae shrink upon cooling of the collagen, thus tightening the chordae and preventing further prolapse. After the thermal irradiation of the chordae has ceased, the rod and cable can be withdrawn fully, or partially into the sheath, and the catheter device can be repositioned above or below the first treated area of the chordae for further treatment or removed entirely.
In a preferred embodiment, the distal end of the cable can be encased in an asymmetric, energy-transmissive balloon attached to the distal end of a catheter. For treatment of atrioventricular valve malfunction, such as primary mitral valve regurgitation, the balloon-tipped catheter device can be moved, with the balloon deflated, into position within the left ventricle using either a conventional guide wire or a guiding catheter, which has been previously inserted into an artery, such as the femoral artery, and advanced through the aorta and the aortic valve into the left ventricle, as is known in the art. The distal end portion of the asymmetric balloon-tipped catheter can be formed into a fixed angle, or the catheter can contain a control element for changing the angle of the distal end portion of the catheter to facilitate precise placement of the asymmetric balloon near or in contact with the chordae.
Likewise, the distal end portion of the device can be positioned near or in contact with the cusps or the annulus of the valve, and the procedure can be carried-out, as described above, to shrink the same.
An optical fiber extends throughout the length of the catheter and is adapted at its proximal end for connection to a source of laser light. The distal end of the optical fiber is positioned opposite the aperture in the distal end portion of the catheter, so that laser light emission from the optical fiber is directed out of an aperture at an angle in the range of about 60 to about 100 degrees from the axis of the fiber. The balloon surrounding the distal end portion of the catheter is asymmetric in shape, having the side of the balloon facing the aperture extending further from the catheter than the opposite side of the balloon. When the balloon is inflated with a fluid that appears opaque under ultrasound or x-ray imaging, the orientation of the balloon within the heart chamber is readily determined. Thus, an image showing the orientation of the greater inflated side of the balloon also indicates the direction of energy emission to the operator.
The balloon catheter can encompass lumens for acceptance of a guide wire, and/or a hooked stabilizing rod such as is described hereinabove. The catheter can also include thermocouples to measure the temperature of the tissue being irradiated and/or the inflation fluid within the balloon.
The proximal end of the balloon catheter preferably comprises a handpiece adapted for delivering inflation fluid through the catheter and into the balloon through the aperture in the distal end portion of the catheter The handpiece can also contain a mechanism for controlling the angle of the distal end portion of the catheter for more precise positioning of the balloon within the tissue.